The present invention relates to automatic electric circuit breakers, particularly those equipped with static or electronic trip units.
In recent years, increasing numbers of industrial molded case circuit breakers are being equipped with electronic trip units, rather than the traditional magnetic and/or thermal trip units. Electronic trip units have the distinct advantage in the precision in which the tripping parameters can be established in terms of overcurrent thresholds and time delays. Also, such electronic trip units readily lend themselves to a convenient user adjustability of the tripping parameters, such that precise tailoring of circuit protection to a particular application is readily obtainable.
Moveover, electronic trip units are typically readily removable from the molded case for convenient servicing and replacement. This latter attribute does however pose a potential hazard. If a circuit breaker is inadvertently put into service without its electronic trip unit, it becomes a non-automatic circuit breaker or switch wholly incapable of affording overcurrent protection.
It is accordingly an object of the present invention to provide an improved static trip molded case circuit breaker.
An additional object of the invention is to provide a static trip circuit breaker of the above character, which can not be inadvertently implemented in the absence of its electronic trip unit.
Yet another object is to provide a circuit breaker of the above character, which includes a trip interlock for preventing closure of the circuit breaker contacts in the absence of the electronic trip unit.
A further object is to provide a circuit breaker of the above character, wherein the trip interlock operates automatically to trip the circuit breaker in response to the removal of the cover of its molded case.
Other objects of the invention will in part be obvious and in part appear hereinafter.